Lightweight impact resistant panel

ABSTRACT

A Hollow lightweight panel made of high tensile strength rigid material. The panel comprises multiple parallel elongated cavities. The cavities are sealed and pressurized with gas. The gas pressure acts to resist any deformation of the panel and thereby reinforces and stabilizes the structure. The panel is suitable for use as structural element in aircraft, spacecraft and road vehicles. The panel is especially effective as armor element, as a lightweight backing for hard layers and as rigid under belly and side panels where required to be resistant to bomb and mine blasts.

PRIORITY INFORMATION

This National Stage Entry claims priority to Israeli Patent No: 209950 filed on Dec. 13, 2010.

FIELD OF THE INVENTION

This invention is in the field of vehicle structural element and anti ballistic armor.

Definitions

In this description an incompressible fluid will refer to a liquid or other substance that will undergo small volumetric change when subjected to high isostatic pressure, and the material will not remain solid, and flow, when subjected to shear forces, for example: water, oil, slurry, paste, sand, ceramic powder and tar.

In this description a fluid will refer to a gas, a liquid or incompressible fluid as described above.

In this description a vehicle will refer to space, ground, air, and water borne vehicles like cars, drones, airplanes satellites, tanks and ships.

BACKGROUND OF INVENTION

Inflatable structures are known to be used in tents made of impervious fabric in the form of interconnected long gas tight chambers. This structure is only at its functional shape and rigid when inflated.

When deflated the structure is not stable it collapses and looses its useful shape.

In patent application WO2007064367 an armor apparatus is disclosed that comprises a layer of parallel pressurized tubes that contain fire retardant, among other chemicals, Silicon gel is interposed between the tubes.

The tubes while providing structural rigidity along their length provide little or no substantial rigidity in lateral direction.

Many types of lightweight panels are used in the field of aviation, vehicles structure and armor that employ a lightweight core sandwiched between two sheets made of metal or fiber reinforced plastic, (FRP).

The core holds the sheets apart and thus provide high bending moment of inertia to the panels.

When trying to design a lighter panel structure, the first choice is to increase the core width and to reduce the width of the peripheral skin surfaces; this will increase the overall moment of inertia while maintaining the weight low.

However the increase of the width of the core and the reduction of the thickness of the peripheral surfaces causes a reduction in the panel stability and the panel may buckle locally when loaded.

The lightweight core can be for example a honeycomb of Aluminum foil, rigid foam, Balsa wood and metal fin structure.

Hollow extruded panels, where a fin structure and enclosing peripheral sheets are extruded as one unit, are also known.

When pressure or bending moment is applied to such a panel, the core is compressed. In order to maintain the peripheral sheets apart under this compression, the core must be strong and rigid.

When the core fails due to local buckling or other deformation, the peripheral sheets become attached, the panel's moment of inertia is reduced and the panel losses it's high rigidity. It is the purpose of the present invention to provide a lightweight rigid and impact resistant panel to vehicles and to lightweight armor arrangements. This purpose is achieved in part by increasing the stability of panels that comprise thin and normally low stability skin surfaces.

SUMMARY OF THE INVENTION

It is to be understood that both the foregoing general description and the following detailed description present embodiments of the invention and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the invention and, together with the description, serve to explain the principles and operations of the invention but not to limit the invention to these descriptions only.

The present invention relates to lightweight panel comprising at least two peripheral skin surfaces made of high tensile strength material. The panel comprises a lightweight core interlayer. In this invention the core interlayer is characterized in comprising a pattern of sealed gas pressurized cavities. The core interlayer further comprises a high strength structure which defines the cavities and holds the skin surfaces in place against the action of the gas pressure.

The core interlayer pattern can be, for example, a series of parallel cavities, a fined structure like honeycomb, or random pattern shaped metal foam.

Unlike the inflated tent structure, the gas pressure is not essential to obtain the panel's shape, its main contribution is hidden from the eye and it is manifested in a favorable stress regime which develops in the structure and increases its stability.

The increased stability also enables to design a lighter and more rigid panel with thinner peripheral surfaces and with lighter or thicker core.

In one preferred embodiment of the present invention, panels are chosen to have skin surfaces and a core pattern with parallel cavities made of the same material, it can sometimes be advantageous to form such a panel by extrusion or pultrusion.

In this embodiment, the boundary between the core and the peripheral surfaces can sometimes be hard to define.

Each cavity is sealed with appropriate plugs that are provided at the each cavity edge.

Pressurized gas or air can be introduced into the cavities through valves that can be fitted to the plugs.

ihe gas pressure can also be monitored and maintained periodically through such valves. When the core cavities are pressurized, tension develops in the peripheral skin surfaces and in the core solid structure pattern, This pressurization increases the stability of the structure. It is the purpose of this invention to provide a lightweight panel of high stability and high resistance to local buckling, to be used in structural element in vehicles, like car doors that are safer against collisions.

The panel of the present invention can be used in aircraft, spacecraft and missile skins.

The panel can easily be shaped to be single curved or cylindrical.

It is the further purpose of this invention to provide a lightweight panel of high stability, high resistance to local buckling and high resistance to impact, to be used in armoring element in vehicles and in personal body armor.

The use of gas pressurization to provide pre-stress to armor panel has the following advantages:

Pressurized gas is lightweight.

In the high pressure gas cavities the gas acts to absorb energy from external penetrating objects,

The tensioned peripheral skins walls have increased lateral wave velocity and increased ductility; this increases the amount of energy that can be absorbed in high velocity impact. U.S. Pat. No. 5,275,873 reveals that a remarkable 23 percent increase in V50 values was observed by subjecting Kevlar® fabrics to tension during ballistic tests.

When the panel's core comprises long cavities, a lost in cavity pressure can cause a weakening of the panel.

A rupture in the panel's skin can also cause a harmful discharge of energetic gas. In order to reduce this risk, the present invention provides an embodiment that comprises self sealing cavity means. These means can avoid or delay the discharge of gas in case of a small rupture. One method of obtaining a self sealing cavity is to dispose lightweight sealers that would conform to the shape of the cavity's cross section and that would be allowed to move in the cavity.

In an event of a small rupture the sealers would drift in the cavity by the flowing gas towards the hole and seal it.

The sealers are preferably made with some rubber that can deform under pressure and seal a deformed cavity.

Another method of obtaining a self sealing cavity is to dispose separation walls in the cavity; each wall comprises a self sealing valve between the two separated cavity sections.

The self sealing valve would close in case a high pressure difference would occur between the separated sections.

The valve will be open when the pressure difference is small.

The valve will allow the filling and discharging of gas in production and maintenance and would stop or delay the gas discharge in case of a local rupture.

The pressures that can be practiced are from about 1 MPa for thin walled panels to pressures in the order of 100 Mpa for compact thick walled ballistic resistant panels.

Creep, tensile strength, fatigue and temperature and work regime are to be taken into consideration when designing a panel.

In another preferred embodiment of the invention a lightweight panel comprising at least two peripheral skin surfaces made of high tensile strength material. The panel comprises a lightweight core interlayer. In this embodiment the core interlayer is characterized in comprising a pattern of sealed cavities pressurized with incompressible fluid. When using water for example instead of pressurized gas, a burst of a panel would be much less energetic and therefore safer.

Another advantage of using a incompressible fluid is that the panel's cavities self pressurize when the panel is subjected to impact or deformation. This phenomenon is used by those who bend tubes by filling them first with sand or liquid.

In this embodiment the incompressible fluid disposed in the panel's core sealed cavities can increase its stability even without pre-pressurizing it.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the invention and together with the description, serve to explain by way of example only, the principles of the invention:

FIG. 1 is a schematic depiction in isometric projection with sectional view of a hollow lightweight panel made of high tensile strength rigid material.

The panel's core comprises multiple parallel elongated cavities.

The cavities are sealed and pressurized with gas; the cavities are cylindrical and arranged in parallel in a single layer.

FIG. 2 is a schematic depiction in isometric projection with broken view of a hollow lightweight panel made of high tensile strength rigid material.

The panel's core comprises multiple cylindrical elongated cavities.

The cavities are sealed and pressurized with gas, the cavities arranged in parallel in two layers.

FIG. 3 is a schematic depiction in isometric projection with broken view of a hollow thin walled lightweight panel made of high tensile strength rigid material.

The panel's core comprises multiple cavities.

The cavities are sealed and pressurized with a gas; the panel comprises a pattern of elongated cavities and fins arranged in parallel in a single layer.

FIG. 4 is a schematic depiction in isometric projection with sectional view of a hollow lightweight cylindrical shaped panel, made of high tensile strength rigid material.

The panel's core comprises multiple cavities.

The cavities are sealed and pressurized with gas; the board comprises multiple elongated cylindrical cavities arranged in parallel to the main cylindrical panel's axis.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As will be appreciated the present invention is capable of other and different embodiments than those discussed above and described in detail below, and its several details are capable of modifications in various aspects, all without departing from the spirit of the invention. Accordingly, the drawings and description of the embodiments set forth below are to be regarded as illustrative in nature and not restrictive.

FIG. 1 is a schematic depiction in isometric projection with sectional view of a hollow lightweight panel 11 made of high tensile strength rigid material preferably by an Aluminum alloy extrusion.

The panel's core comprises multiple parallel elongated cavities 10.

The cavities 10 are sealed and pressurized with gas; the cavities are cylindrical and arranged in parallel in a single layer.

The cavities are sealed by plugs (not shown) at their ends; each cavity is fitted with a filling valve (not shown).

FIG. 2 is a schematic depiction in isometric projection with broken view of a hollow lightweight panel 21 made of high tensile strength rigid material.

The panel's core comprises multiple cylindrical elongated cavities 20.

The cavities are sealed and pressurized with gas; the cavities are arranged in parallel in two layers.

The cavities are sealed by plugs (not shown) at their ends; each cavity is fitted with a filling valve (not shown).

FIG. 3 is a schematic depiction in isometric projection with broken view of a hollow thin walled lightweight panel 31 made of high tensile strength rigid material.

The panel's core comprises multiple cavities 30.

The cavities are sealed and pressurized with a gas; the panel comprises a pattern of elongated cavities and fins 32 arranged in parallel in a single layer.

The shape of the cavity is chosen as the shape that would provide the maximum volume for given fin and cavity perimeter length.

The cavities are sealed by plugs (not shown) at their ends; each cavity is fitted with a filling valve (not shown).

FIG. 4 is a schematic depiction in isometric projection with sectional view of a hollow lightweight cylindrical shaped panel 42 comprising an internal main surface 41, made of high tensile strength rigid material.

The panel's core comprises multiple cavities 40.

The cavities are sealed and pressurized with gas; the board comprises multiple elongated cylindrical cavities arranged in parallel to the main cylindrical panel's axis.

The cavities are sealed and interconnected (not shown) at their ends; the cavities are fitted with a filling valve (not shown).

This embodiment can reduce the weight is rocket skin envelopes where high rigidity and low weight are critical. 

1. A lightweight impact resistant panel comprising; a) Two peripheral skin surfaces made of high tensile strength material, and b) a lightweight core structure is disposed between the two skin surfaces, and attached to the skin surfaces, wherein c) the core comprises a pattern of sealed fluid pressurized cavities containing a fluid, and d) whereby the pressure in the cavities increases the stability of the structure against buckling, and makes the structure more resistant to impact.
 2. A lightweight impact resistant panel comprising; a) Two peripheral skin surfaces made of high tensile strength material, and b) a lightweight core structure is disposed between the two skin surfaces, and attached to the skin surfaces, and, c) the core comprises a pattern of sealed cavities, and d) the cavities are filled with an incompressible fluid, and e) wherein the panel's cavities self pressurize when the panel is subjected to Impact, whereby the pressure in the cavities increases the stability of the structure against buckling, and makes the structure more resistant to impact.
 3. A lightweight impact resistant panel according to claim 1 wherein the fluid is a gas.
 4. A lightweight impact resistant panel according to claim 1 wherein the panel is comprised in an anti ballistic armor arrangement.
 5. A lightweight impact resistant panel according to claim 1 wherein the panel is comprised in a vehicle structural body arrangement.
 6. A lightweight impact resistant panel according to claim 1 wherein the panel's core and peripheral surfaces is formed by metal extrusion and are of a constant sectional shape.
 7. A lightweight impact resistant panel according to claims 1, wherein the panel's core and peripheral surfaces is formed by FRP pultrusion, and are of a constant sectional shape.
 8. A lightweight impact resistant panel according to claim 6, wherein the panel comprises self sealing means.
 9. A lightweight impact resistant panel according to claim 7, wherein the panel comprises self sealing means.
 10. The lightweight resistant panel of any claims 1 wherein the cavities comprise valves for pressurizing. 